1. Field of the Invention
The present invention relates to techniques for planning a stenting procedure, including selection of an appropriate stent, and for conducting the stenting procedure, in which the stent is implanted in a subject at an appropriate location.
2. Description of the Prior Art
The use of percutaneous coronary interventions, particularly stenting procedures, has become the treatment of choice for many manifestations of coronary artery disease.
Stenting procedures also are widely performed to treat stenosis in blood vessels other than the coronary arteries, such as the renal artery or the mesenteric artery, or other peripheral vessels.
Although stenting greatly enhances the patient's quality of life by relieving the patient's symptoms and reducing ischemia almost immediately, this technique has not proven to be completely successful on a long-term basis for many patients. The lack of success in some patients is due to a phenomenon known as restenosis inside or near the stented area. The occurrence of restenosis is often due to a misplacement of the stent, or a sub-optimal choice of the stent type or stent size.
The stent type and size are determined by the physician performing the stenting procedure based on measurements of the size and extent of the lesion area obtained from an angiography x-ray projection (image). Since an angiography x-ray projection is a 2D image, however, and it is being used to measure a 3D structure, a 3D structure that is not substantially completely in the plane of the angiography projection will appear foreshortened in the 2D image.
Moreover, stent placement is performed based on visualization of the stent delivery catheter on a real-time 2D x-ray projection acquired without contrast agent injection. This means that the lesion most likely will not be clearly visible in this real-time 2D x-ray projection, and thus the physician must place the stent somewhat blindly when the physician considers the stent delivery catheter to be correctly placed based on the physician's memory of the vessel anatomy (obtained from a previous x-ray projection using contrast agent injection). Again, foreshortening of 3D objects in the 2D x-ray projection can impair the correct placement of the stent delivery catheter.
To improve the accuracy of such lesion measurements, it is known to generate a 3D reconstruction of the lesion-containing region of the patient based on multiple 2D x-ray projections of the diseased vessel. In such a 3D reconstruction, it is possible to measure the lesion size and extent three-dimensionally, which significantly reduces errors due to the foreshortening effect. As a consequence, selection of the appropriate stent to treat the lesion in question is improved.
Other techniques are known to control the position and expansion of the stent in the diseased vessel. For example, post-processing algorithms are known that enhance the visualization of a stent (particularly the stent struts) in a 2D x-ray projection. Intravascular ultrasound (IVUS) techniques as well as optical techniques such as optical coherence tomograph (OCT) are also known and used to assist in visualizing the stent relative to the vessel wall. These techniques, however, are used post-interventionally (after the stent placement). At this point, the implanted stent cannot be removed and cannot even be shifted to a better location within the vessel. This means that if the stent is not correctly placed in the stenting procedure, a second stent may have to be implanted to better treat the lesion area.